(1) Field of the Invention
The present invention relates to a method of repairing a shed portion of a composite insulator having a core portion, a sheath portion arranged on an outer surface of the core portion, and shed portions projected from the sheath portion. In this invention, a term "composite insulator" means a wide concept such that it includes not only a polymer insulator having the core portion made of for example FRP rod but also a polymer hollow insulator, a hollow SP insulator, or the like each having the core portion made of for example FRP cylinder.
(2) Related Art Statement
FIG. 10 is a cross sectional view showing one embodiment of a polymer insulator as one example of a composite insulator to be repaired. In the embodiment shown in FIG. 10, a polymer insulator 1 comprises an FRP core 2, a sheath portion 3 arranged on an outer surface of the FRP core 2, and a plurality of shed portions 4 projected on said sheath portion 3. In the polymer insulator 1 mentioned above, the sheath portion 3 and the shed portions 4 made of for example silicone rubber are integrally formed on an outer surface of the FRP core 2 by means of a metal mold not shown. In the case of forming the polymer insulator 1, it is known that defects such as inclusion of foreign substances and non-cured portion are liable to be generated at a periphery of the shed portion.
As mentioned above, the polymer insulator 1 to be repaired according to the invention has a plurality of shed portions 4. Therefore, if defects are generated in one shed portion 4 after producing the polymer insulator 1 or during an actual use of the polymer insulator 1, an overall polymer insulator 1 becomes a defect product and thus is scrapped together with the shed portions 4 having no defects, so that a using efficiency of the polymer insulator 1 is decreased. Moreover, since the overall polymer insulator 1 must be scrapped even if it has many normal shed portions 4, an amount of scrapped polymer insulators 1 is increased. In addition, if the polymer insulator 1 to be scrapped has a long size, scrapping steps are increased. As a result, labor, cost and so on for scrapping the polymer insulators 1 having defects are also increased.
In order to solve the drawbacks mentioned above, it is possible to think an idea such that the polymer insulator 1 is designed on the basis of a higher safety rate or that a new method of producing the polymer insulator 1 having no defects is realized. However, if the polymer insulator 1 is designed on the basis of a higher safety rate, raw materials are wasted and an amount of the scrapped polymer insulators are increased in the same manner as the above mentioned embodiment in which the overall polymer insulators having defects are scrapped, so that it is not possible to produce the polymer insulator 1 in a highly efficient manner. Moreover, it takes a lot of times and cost so as to realize the new method of producing the polymer insulator having no defects. Therefore, the known techniques can not solve the drawbacks mentioned above basically.